Osmotic devices for delivering a beneficial agent formulation, including a medicine, to an enivornment of use are known to the prior art in U.S. Pat. No. 3,845,770 issued to Theeuwes and Higuchi, and in U.S. Pat. No. 3,916,899 issued to the same patentees. The osmotic devices disclosed in these patents comprise a semipermeable wall that surrounds a compartment containing a beneficial agent formulation including a medicinal formulation. The semipermeable wall is permeable to the passage of an external fluid present in the environment of use and it is substantially impermeable to the passge of a beneficial agent formulation. An osmotic passageway is provided through the wall for delivering the beneficial agent formulation from the osmotic device. These prior art devices release the beneficial agent formulation by imbibing fluid through the semipermeable wall into the compartment to form in the compartment an aqueous solution containing the beneficial agent formulation that is delivered through the passageway from the osmotic device. The external fluid is imbibed through the semipermeable wall into the compartment in a tendency towards osmotic equilibrium at a rate determined by the permeability of the semipermeable wall and the osmotic pressure gradient across the wall. These devices are extraordinarily effective for delivering a beneficial agent formulation that is soluble in the fluid and exhibits an osmotic pressure gradient across the semipermeable wall against the external fluid. These osmotic devices are extraordinarily effective also for delivering a beneficial agent formulation that has limited solubility in the external fluid and is admixed with an osmotically effective osmagent that is soluble in the fluid and exhibits an osmotic pressure gradient across the semipermeable wall against the fluid. The beneficial agent formulation is incorporated into these osmotic devices during their manufacture, prior to forming the semipermeable wall around the compartment. These prior art osmotic devices operate successfully for delivering a beneficial agent formulation including a beneficial medicinal formulation to an environment of use.
A pioneering advancement in osmotic delivery devices was presented to the dispensing art by Cortese and Theeuwes in U.S. Pat. No. 4,327,725. In this patent, the delivery kinetics of the osmotic device are enhanced for delivering beneficial agents with degrees of solubility in aqueous films that are difficult to deliver, such as very soluble or insoluble in the fluid. For these beneficial agents, the delivery kinetics are enhanced by placing in the compartment an expandable driving member that urges the agent formulation through a passageway from the device. The expandable driving member is formed of a water-expandable hydrogel that absorbs fluid imbibed into the compartment and expands from a rested to an expanded state. The hydrogel is in contact with the agent formulation with the hydrogel positioned distant from the passageway. As the hydrogel absorbs fluid it increases in volume causing it to exert force against the agent formulation, thereby urging the agent formulation through the passageway over time.
The osmotic passageway, in the osmotic device described immediately above, is laser drilled through the semipermeable wall to connect a beneficial agent dye-free formulation with the exterior of the osmotic device. The osmotic passageway is laser drilled in this predetermined location by orienting the osmotic device such that the laser drills a passageway only at this loci. This orientation is made possible by adding a dye to the expandable hydrogel and then scanning the exterior of the osmotic device for a difference in shade between the beneficial agent dye-free formulation and the expandable dye-containing hydrogel. The presence of the dye imparts a shade to the expandable hydrogel exhibited as a comparative darkness as seen through the translucent semipermeable wall.
The above described prior art procedure is remarkably successful for laser drilling the osmotically calibrated passageway, even though it requires the use of a comparative light-producing agent, visual observation, or optical scanning for positioning the osmotic device. It will be appreciated, by those versed in the dispensing art, that if an osmotic device is provided that does not require the orientation, or the agent, or the scanning techniques of the prior art, such an osmotic device would represent an inventive contribution and an unobvious and a practical advancement in the dispensing art.